The invention relates to apparatus for surface grinding of metal and alloy workpieces, particularly titanium and titanium-base alloy workpieces such as slabs and billets.
In the production of titanium, including titanium alloy, workpieces such as slabs and billets it is necessary to condition the surface of the workpiece for removal of surface defects prior to further processing of the workpieces. This is conventionally achieved by a surface grinding operation. In typical operations of this type, a grinding wheel is used to either grind a substantially uniform layer from the entire surface of the workpiece or in the alternative surface defects are located, marked and then selectively removed by grinding. With titanium workpieces, because of the pyrophoric nature thereof, excessive amounts of smoke or fumes are produced during surface grinding. To prevent contamination of the grinding area, it is necessary that these fumes be removed as grinding proceeds.
With grinding operations of this type, the grinding wheel performing the grinding function is brought into contact with the workpiece surface and is directed to traverse the surface in oscillating fashion until the grinding operation is completed. In operations of this type, it is known to cover the workpiece during grinding with a stationary hood with the hood being connected through ductwork and an exhaust fan for removing the fumes from the hood to a discharge area, typically a bag-house. Since the workpieces being conditioned are relatively large, stationary hoods must be correspondingly large. This results in a large volume of air, typically 35,000 cfm to 50,000 cfm, to be exhausted by the exhaust system. This in turn requires large-capacity bag-houses for collection and also high capacity motors and fans for withdrawing the fumes.
It is also known to use hoods that travel or oscillate with the grinder during the surface grinding operation. These hoods provide difficulty, however, with respect to effective connection of the duct for discharge of the fumes to the location apart from the hood. To permit movement of the duct with the hood it is typical to connect the end of the duct opposite the end connected to the hood to a fixed, elongated conduit by means of an open connection with the end of the duct sliding along the conduit at the open connection. This results in leakage of the fumes at the open connection. Also, with travelling hoods of this type if they are designed for minimum interior volume to in turn minimize the needed capacity of the duct and exhaust system the swarf produced during the grinding operation causes rapid deterioration of the hood. Specifically, during grinding of titanium workpieces a large amount of high-temperature swarf is removed which swarf travels at high velocity and in typical fashion impinges against the interior portions of the hood to result in rapid deterioration thereof. Also, with conventional systems this swarf collects within the hood and thus requires a hood drive of sufficient capacity to move not only the hood with the grinder but also the swarf collected within the hood. In addition, with conventional systems the swarf is removed from the hood by the exhaust system and passes through the conduit to the bag-house. The swarf is at a temperature of approximately 3,000.degree. F. and if exhausted with the fumes may ignite in the ductwork or the bag-house. In addition, such requires a large bag-house capacity to collect the relatively large swarf particles along with the fumes.